Ph1-positive acute myelocytic leukemia with high TdT levels

Surface marker analysis and karyotype distinguish acute biphenotypic leukemia from acute myelogenous leukemia expressing terminal deoxynucleotidyl transferase

Surface phenotyping by flow cytometry and cytochemical study were used to identify 15 adult patients with acute leukemia displaying ambiguous phenotypes. Differences were found in the blast cell karyotype and immunoglobulin gene rearrangements of terminal deoxynucleotidyl transferase (TdT)-positive acute myelogenous leukemia (AML) and biphenotypic leukemia expressing B lymphoid and myeloid markers. The karyotypic abnormalities, t(9;22) and t(4;11), were noticed in acute biphenotypic leukemia, and were consistently associated with rearrangement at the immunoglobulin locus. Furthermore, coexpression of CD19/CD20 and either myeloperoxidase or myeloid surface markers were predictive of finding the t(9;22) or t(4;11) karyotype. Patients with TdT-positive AML, on the other hand, were less likely to show rearrangement at the immunoglobulin locus, and did not have the t(9;22) or t(4;11). Instead, a variety of nonrandom karyotypic abnormalities were seen, including trisomy 13. Unlike common AML, the majority of TdT-positive cases demonstrated an abnormal karyotype with duplications and/or deletions present in all cases. In no instance was trisomy 8, t(8;21), t(15;17), or any other isolated translocation identified. The authors therefore suggest that immunophenotyping, when combined with cytochemical analysis of TdT and myeloperoxidase or Sudan black B, may aid in the characterization of subgroups of atypical acute leukemia, such that alternate approaches to therapy can be evaluated.

Effects of antileukemic agents on the activity of terminal deoxynucleotidyl transferase from human normal thymic and leukemic cells "in vitro"

Several widely used and experimental antileukemic drugs have been tested on the activity of Terminal deoxynucleotidyl Transferase (TdT) purified from normal human thymocytes and T-derived acute lymphoblastic leukemia peripheral blood lymphoblasts. The majority of these inhibitors were equally potent inhibitors of the enzyme from thymocytes or leukemic lymphocytes. Adriamycine and etoposide were more potent inhibitors of the enzyme purified from thymocytes. Vincristine was a more potent inhibitor of TdT extracted from leukemic lymphocytes than from thymocytes. These results are discussed in terms of possible functions for TdT in the two types of cells and on the value of TdT as an indicator for clinical treatment.

Phenotype of the terminal transferase-positive cells in human foetal liver and bone-marrow: analysis with monoclonal antibodies

Liver and bone-marrow of 20 human foetuses between 15th and 20th week of gestational age were examined. Mononuclear cells were labelled with murine monoclonal antibodies to reveal surface antigens and with a rabbit antiserum to TdT for the detection of the nuclear enzyme, using a double colour indirect immunofluorescence technique. The results have revealed that TdT+ cells express the phenotype of B cell precursors HLA-DR+, CALLA+, FMC8+, LEU-1-, LEU-5-, LEU-9-. It suggests that foetal liver and bone-marrow have an active function in B-lymphopoiesis in humans. The involvement of TdT in the process of B-cell immunological acquisition is uncertain because only humans and Xenopus embryos, among the species examined, express TdT outside the thymus during ontogenesis.

Terminal deoxynucleotidyl transferase (TdT) in human foetuses. An immunofluorescent and biochemical study

The liver, bone marrow and cord blood of 30 human foetuses between the 15th and 21st weeks of gestational age were examined. Liver suspensions were investigated both by immunofluorescent and biochemical assay; cord blood suspensions and bone marrow touches with immunofluorescent assay. The results indicate the existence of a few TdT+ cells in the liver, cord blood and bone marrow of human foetuses in the ages studied. The peaks for each organ were: 15 +/- 1.60 (mean +/- SD) TdT+ cells in the liver, 12 +/- 2 in the bone marrow and 18 +/- 2.83 in the cord blood. In all the organs TdT+ cells decrease in the later weeks. In the liver, the results of the immunofluorescent assay were confirmed by the biochemical activity.